In one aspect, the invention relates to a fiber mat suitable for incorporating into a molding composition. In another aspect, the invention relates to a process for forming the fiber mat. In yet another aspect, the invention relates to molding composition containing the fiber mat.
For many applications, it is desirable to provide finished parts with electromagnetic interference (EMI) shielding characteristics. In the automotive field, EMI shielding is required for plastic hoods, fenders, and fire walls. Office business machines require some form of shielding over parts of their internal areas. By regulation, emissions from all digital computing devices must be within certain radiation limits. Regulation of emissions is necessary because of increasing complaints of electrical malfunctions caused by electromagnetic interference. Examples include TV snow, flight instrument malfunctions caused by pocket calculators and activation of electrically controlled devices by citizen band radios.
Methods presently used to shield electronic components have been ranked in order of preference. The methods, in order of preference, include silver paint application, nickel paint application, conductive filler utilization, silver reduction, cathode sputtering, foil application, copper paint, vacuum metalizing, electroplating, flame/arc spraying and graphite paint application. With the exception of conductively filled plastics, all of the shielding methods suffer from either a limited life due to chipping, cracking, peeling or the fact that they involve costly secondary operations.
The most desirable method of shielding is with conductively filled plastic because the shielding material is an integral part of the plastic and will not chip or blister and does not require a secondary operation. However, incorporating conductive fillings in plastics frequently reduces product properties in an unacceptable extent because of the high amount of filler required to provide acceptably high shielding characteristics.